If Richards stumbles badly tonight and has to be pulled early. Houck could be the long reliever, and the other four starters would simply get regular rest and not an extra day's rest. Long reliever Valdez pitched 2.1 innings last night. However, Whitlock last pitched 4 days ago (July 23) and just 1 inning.
I doubt Houck will be used tonight because Cora and Bloom both need to know how effective he is as a starter because they must have doubts about Richards, Perez, and ERod.